Ruth K. Varner Carmody K. McCalley Clarice R. Perryman Mika Aurela Sophia A. Burke Jeffrey Chanton Patrick Crill Jessica DelGreco Jia Deng Liam Heffernan Christina Herrick Suzanne B. Hodgkins Cheristy P. Jones Sari Juutinen Evan S. Kane Louis J. Lamit Tuula Larmola Erik Lilleskov David Olefeldt Michael W. Palace Virginia I. Rich Christopher Schulze Joanne H. Shorter Franklin Sullivan Oliver Sonnentag Merritt R. Turetsky Mark Waldrop McKenzie A. Kuhn 2024 <p>Northern peatlands are a globally significant source of methane (CH₄), and emissions are projected to increase due to warming and permafrost loss. Understanding the microbial mechanisms behind patterns in CH₄ production in these systems will be key to predicting annual emissions changes, with stable carbon isotopes (δ¹³C-CH₄) being a powerful tool for characterizing these drivers. Given that δ¹³C signatures of CH₄ are used in top-down atmospheric inversion models to partition sources, our ability to model CH₄ production pathways and associated δ¹³C-CH₄ signatures in peatland types impacted by a changing climate is critical. We sought to characterize the role of environmental conditions, including both hydrologic and vegetation patterns associated with permafrost thaw, on δ¹³C-CH₄ signatures from a diverse set of high-latitude peatlands. We measured porewater and emitted CH₄ stable isotopes, pH, and vegetation composition from five boreal-Arctic peatlands. Porewater δ¹³C-CH₄ was strongly associated with peatland type, with δ¹³C enriched values obtained from more minerotrophic fens (-61.2 ± 9.1‰) compared to permafrost-free bogs (-74.1 ± 9.4‰) and raised permafrost bogs (-81.6 ± 11.5‰). Variation in porewater δ¹³C-CH₄ was best explained by sedge cover, CH₄ concentration, and the interactive effect of peatland type and pH (<i>r</i>² = 0.50, p &lt; 0.001). Emitted δ¹³C-CH₄ varied greatly but was positively correlated with porewater δ¹³C-CH₄, suggesting that porewater data can be used to predict changing emissions signatures from these systems. We calculated a weighted mean mixed atmospheric CH₄ signature for northern peatlands of -65.3 ± 7‰ and show that this signature is more sensitive to landscape drying (4 to 10 % depletion in δ¹³C) than wetting (1.5 to 5% enrichment in δ¹³C) under permafrost thaw scenarios. Our results suggest northern peatland δ¹³C-CH₄ signatures are likely to shift in the future which has important implications for source partitioning in atmospheric inversion models.</p> application/pdf 10.1029/2023JG007837 en American Geophysical Union Controls on stable methane isotope signatures in northern peatlands and potential shifts in signatures under permafrost thaw scenarios article